The Impact of Sea Level Rise on China's Coastal Areas and Its Disaster Hazard Evaluation

Abstract

The coastline of China stretches for about 18,000 km. China's coastal areas concentrate 70% of big cities and 41% of the total population of the nation. Fifty-five percent of the gross national product and 65% of the national industrial output are made in these areas. Although the areas occupy less than 1/7 of the total territory of China, they create more than half of the national wealth. China's coastal areas can be acclaimed as China's "wealth-belt", "lifebloodbelt". However, most of the areas are low-lying lands with relatively gentle topography. The possible harmful impact caused by the relative sea level rise on the area is studied. This study includes the increase in occurrence frequency of storm surge and flood; the extension of inundation of low-lying land; the acceleration of paralyzation of the existing drainage system; the intensification of erosion and retreat of sea shore; and the increase of the submergence of coastal areas, salt intrusion and the pollution of fresh water resources. Several factors concerning the disaster hazard evaluation for coastal areas resulting from sea level rise are discussed. They include: adopting under-estimated value of sea level rise rate; taking the economic and social developments of a coastal area as a threshold of the hazard evaluation for the area; combining sea level rise with crustal vertical movement; taking account of the capability and adequacy of the protection facilities. The index for these factors and a method of integrative hazard evaluation are presented. Finally, the data for the Chinese regional sea level rise in recent years are also summarized in the paper. The estimated value of future relative sea level rise rate in some main coastal areas of China is 5-8 mm/a. This means that the relative sea level rise in the areas may reach 30-45 cm by 2050 in general, and in a few areas, such as the Old Yellow River Delta, may be 70-80 cm.